Enzymatic dispersion of tumors and cell fractionation will be used to assist in the identification of the relevant cellular and humoral host effector mechanisms involved in the rejection of the solid T1699 mammary tumor. Tumor specific immunity inside the tumor and in the peripheral blood will be measured (as well as nonspecific indicators of immunity) in animals with progressor and regressor tumors in an attempt to identify the relevant assay for monitoring the host response. We also wish to continue investigations of the protective serum factor present in tumor bearing animals (assayed by passive transfer) and wish to identify the factor (antigen-antibody complex?) by chromatographic methods, and to investigate the uniqueness of this factor; (solely in the T1699 mammary tumor or also present in the spontaneous C3H mammary tumors?). With the aid of immunologically compromised and reconstituted animals the project will also identify the origin of the colony inhibiting cells in the tumor and the origin of the cells producing and mediating rejection by the humoral substance. The kinetics of cellular infiltration into both progressor and regressor tumors will be studied. This should lead to a better understanding of the host reaction to the growing tumor and also to an improved approach to combination and individualized therapy.